Once again, the man who once captured the imaginations of millions delivered an emotionless appeal.

It was the most tweeted about political event of the year, and for once the insider tweets matched the television insta-polls: Mitt Romney was the decisive victor in the first presidential debate of this most contested and close of elections.

It was not so much that Romney was great, though he was smooth and personable, but that Obama was not. The president appeared snippy, his eyes flashing angrily during those infrequent moments when he looked at his opponent, his lips pursed and upturned when he looked down -- which was often -- as if he were trying to smile despite sucking on a particularly unpleasant hard candy. Republicans on Thursday morning were calling it a smirk, but it was more than that. There was, in the expression, a mixture of annoyance, impatience, and dislike. Either Obama couldn't stand looking at Romney, or he decided it was a better debating tactic to not even deign to consider him and to address hapless moderator Jim Lehrer and the audience instead of his challenger. The dynamic was set early on: Romney looked at Obama, and Obama looked down or at the moderator. His words appeared equally downbeat.

All of which made me wonder anew about Obama's convention performance, and to what an extent it was not anomalous but intentional and characteristic. I wrote then:

Barack Obama will never be that man again. Whoever he was in 2008, and 2004, Barack Obama will never have his easy swagger and rambunctiously playful enthusiasm ....

That is the truth at the core of his oddly flat convention speech, and at the center of his technically skilled but strangely bloodless reelection campaign. Whoever Obama was when he was elected president has been seared away by two active wars, the more free-ranging fight against al-Qaeda, the worst economic crash since the Great Depression, and the endless grinding fights with Washington Republicans -- and even, I am sure, activists in his own party.

It seemed even truer last night. Would Obama have gotten so significant a convention bounce if it were just about his own speech? His demeanor in Denver made me wonder if his was not in some important sense a borrowed bounce, bequeathed to him by Bill Clinton.

Many are writing this morning that Obama seemed unprepared, but that's hardly credible. He did not stumble over answers or forget his talking points. Rather, he appeared badly prepared by his handlers to pursue a strategy of non-engagement with Romney while aiming to deliver a passable, above-the-fray presentation. It was a classic frontrunner strategy -- first, do no harm -- but it flopped because Romney was so eager to engage, and chose the occasion of the first debate to showcase a classic Romney policy pivot.

If you reread the pre-debate expectations-setting coverage, it appears Obama did exactly what he was gunning to do:

Obama is not particularly fluid in sound bites, so his team is aiming for a workmanlike performance like his speech at the Democratic convention.

That New York Times piece mentioned something else important to consider:

As the candidates prepare, the first trick for Mr. Obama is finding time. His rehearsals have started late and ended early because of events like the tumult in the Middle East. He showed up at one practice just after speaking at a ceremony for the four Americans killed in Libya, and aides found that his mind was elsewhere.

I said it after the convention speech and I'll say it again: If there's something that seems shut down in our once ebulliently optimistic president, it most likely has to do with the wars. Obama is a naturally empathic individual, whose diverse, mobile, international background made him unusually able when it came to assessing new social situations and reading more than people say. Some observers have speculated that Obama needs a crowd, energy he can draw from. But he had that aplenty in Charlotte, and it barely helped. I suspect a more prosaic explanation: A person of his temperament cannot maintain the same open demeanor when he's dealing with war and death all the time. As, we must recall, Obama has been for years now. If Obama seems shut down, perhaps it is because he has to be to be who he is and do the job he needs to do day in and day out. If his heart didn't seem in it last night, I wonder if it's not in part because the last thing he needs to consider in his work on a day-to-day basis is his heart. It's a long way from being a community organizer, civil-rights lawyer and anti-war state senator to running a drone war that kills innocent civilians, ordering the death of militants, overseeing a policy that's led to an increase in American casualties in Afghanistan, and delivering funereal remarks at a ceremony honoring the returning remains of a slain American diplomat.

It's the only explanation I can come up with for why there is so much self-abnegation in Obama's campaigning. Does it do anything for any sort of voter to hear this, from Obama's closing remarks last night?

You know, four years ago I said that I'm not a perfect man and I wouldn't be a perfect president. And that's probably a promise that Governor Romney thinks I've kept. But I also promised that I'd fight every single day on behalf of the American people and the middle class and all those who are striving to get in the middle class. I've kept that promise and if you'll vote for me, then I promise I'll fight just as hard in a second term.

The emphasis on imperfection, the almost apologetic tone -- it's something that's come and gone in Obama's messaging since before the Republican take-over in 2010.

Romney has had the luxury of being able to campaign undistracted by a day job. More importantly, he's been able to campaign undistracted by dealing with anything substantive or difficult in recent years. Campaigns are physically taxing. But the toll of being president is something different again.

His supporters keep wanting Obama to be who he was in 2008. But that's not who he is anymore.